Economical production of aluminum hydride (AlH3) or “alane” depends on an approach that combines aluminum with hydrogen in a manner that is energy efficient and practical. However, the rate of direct reaction between pure aluminum and hydrogen is very slow. A major barrier to this reaction is that little change in enthalpic energy (ΔHf=−2.37 kcal/mol AlH3) occurs in the transformation of elemental aluminum and hydrogen to aluminum hydride. The ordered nature of the crystalline aluminum metal also inhibits reaction with hydrogen. Another barrier is that the aluminum oxide (Al2O3) coating that forms on the surface of aluminum when it comes in contact with air, reduces or limits the surface area of the reactive aluminum and inhibits the reaction with hydrogen.
The presence of gallium metal and other elements such as indium, mercury, tin, and bismuth in aluminum alloys are known to increase the “aqueous” electrochemical activity of aluminum as a sacrificial anode electrode in cathodic protection systems or in chemical power systems. Activation of aluminum can also occur through the addition of cations such as In3+, Ga3+, Hg2+, Sn4+ and Sn2+ to the electrolyte.